1. Field of the Invention
The present invention generally relates to integrated circuit manufacture, and more specifically, the invention provides a method and system for providing an end point for silicon wafer thinning.
2. Background Art
The use of semiconductor devices in today's commercial goods is undergoing dramatic growth. In order to expand the use of semiconductor devices, these devices must be produced at previously unattainable low cost and with smaller size active devices and smaller line widths. Virtually every step of semiconductor device production is undergoing extensive investigation in an effort to obtain efficiencies and cost savings that will expand the market for semiconductor products.
One of the areas of semiconductor production that receives continuous attention is miniaturization of the devices. In the production of semiconductor devices such as IC cards, solar cells and thin film transistors or semiconductor integrated circuits, miniaturization of devices or degree of freedom concerning use thereof can be improved by making the thickness of semiconductor wafers used as substrates therefor sufficiently thinner.
In a conventional technique, in order to produce a thin semiconductor wafer, semiconductor devices (circuit patterns) are formed on a surface of a mirror-polished semiconductor wafer, then a protective tape is adhered on the surface, the wafer is placed on a chuck table of grinding apparatus with the surface side as the underside, and the back surface of the wafer is ground with a grinding stone to thin the wafer.
The usual thickness of the semiconductor wafer generally varies depending on its diameter and, for example, it is about 625 μm for a wafer having a diameter of 5 inches (125 mm) or 6 inches (150 mm) or about 725 μm for a wafer having a diameter of 8 inches (200 mm). Also, although the thickness after thinning may vary depending on types of semiconductor devices to be produced, that thickness is generally about 150-400 μm.
One important challenge that is faced when thinning the wafers is that, if a wafer is thinned too much, structures that were formed in the wafer may be damaged. One way to address this challenge is to determine beforehand, by using test or sacrificial wafers, the extent to which the backsurface of the wafer should be ground away. This, however, is not a completely satisfactory solution because wafers can vary in thickness. Thus, grinding off a predetermined thickness may result in some wafers being damaged. As a result, varying depth of thickness is needed to achieve proper silicon removal.